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SubjectRe: [PATCH] mfd: cros ec: spi: Fix "in progress" error signaling
Hi Shawn,

On Wed, Sep 27, 2017 at 02:35:27PM -0700, Shawn Nematbakhsh wrote:
> For host commands that take a long time to process, cros ec can return
> early by signaling a EC_RES_IN_PROGRESS result. The host must then poll
> status with EC_CMD_GET_COMMS_STATUS until completion of the command.
>
> None of the above applies when data link errors are encountered. When
> errors such as EC_SPI_PAST_END are encountered during command
> transmission, it usually means the command was not received by the EC.
> Treating such errors as if they were 'EC_RES_IN_PROGRESS' results is
> almost always the wrong decision, and can result in host commands
> silently being lost.
>
> Reported-and-tested-by: Jon Hunter <jonathanh@nvidia.com>
> Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>

Acked-by: Benson Leung <bleung@chromium.org>

> ---
> drivers/mfd/cros_ec_spi.c | 52 ++++++++++++++++++++++-------------------------
> 1 file changed, 24 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
> index c9714072e224..d019b5b00b67 100644
> --- a/drivers/mfd/cros_ec_spi.c
> +++ b/drivers/mfd/cros_ec_spi.c
> @@ -377,6 +377,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> u8 *ptr;
> u8 *rx_buf;
> u8 sum;
> + u8 rx_byte;
> int ret = 0, final_ret;
>
> len = cros_ec_prepare_tx(ec_dev, ec_msg);
> @@ -421,25 +422,22 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
> if (!ret) {
> /* Verify that EC can process command */
> for (i = 0; i < len; i++) {
> - switch (rx_buf[i]) {
> - case EC_SPI_PAST_END:
> - case EC_SPI_RX_BAD_DATA:
> - case EC_SPI_NOT_READY:
> - ret = -EAGAIN;
> - ec_msg->result = EC_RES_IN_PROGRESS;
> - default:
> + rx_byte = rx_buf[i];
> + if (rx_byte == EC_SPI_PAST_END ||
> + rx_byte == EC_SPI_RX_BAD_DATA ||
> + rx_byte == EC_SPI_NOT_READY) {
> + ret = -EREMOTEIO;
> break;
> }
> - if (ret)
> - break;
> }
> - if (!ret)
> - ret = cros_ec_spi_receive_packet(ec_dev,
> - ec_msg->insize + sizeof(*response));
> - } else {
> - dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
> }
>
> + if (!ret)
> + ret = cros_ec_spi_receive_packet(ec_dev,
> + ec_msg->insize + sizeof(*response));
> + else
> + dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
> +
> final_ret = terminate_request(ec_dev);
>
> spi_bus_unlock(ec_spi->spi->master);
> @@ -508,6 +506,7 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
> int i, len;
> u8 *ptr;
> u8 *rx_buf;
> + u8 rx_byte;
> int sum;
> int ret = 0, final_ret;
>
> @@ -544,25 +543,22 @@ static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
> if (!ret) {
> /* Verify that EC can process command */
> for (i = 0; i < len; i++) {
> - switch (rx_buf[i]) {
> - case EC_SPI_PAST_END:
> - case EC_SPI_RX_BAD_DATA:
> - case EC_SPI_NOT_READY:
> - ret = -EAGAIN;
> - ec_msg->result = EC_RES_IN_PROGRESS;
> - default:
> + rx_byte = rx_buf[i];
> + if (rx_byte == EC_SPI_PAST_END ||
> + rx_byte == EC_SPI_RX_BAD_DATA ||
> + rx_byte == EC_SPI_NOT_READY) {
> + ret = -EREMOTEIO;
> break;
> }
> - if (ret)
> - break;
> }
> - if (!ret)
> - ret = cros_ec_spi_receive_response(ec_dev,
> - ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
> - } else {
> - dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
> }
>
> + if (!ret)
> + ret = cros_ec_spi_receive_response(ec_dev,
> + ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
> + else
> + dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
> +
> final_ret = terminate_request(ec_dev);
>
> spi_bus_unlock(ec_spi->spi->master);
> --
> 2.12.2
>

--
Benson Leung
Staff Software Engineer
Chrome OS Kernel
Google Inc.
bleung@google.com
Chromium OS Project
bleung@chromium.org
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